Myths vs facts: HbA1c and sleep

The claim that sleep does not affect HbA1c is a myth. Evidence shows that sleep duration and quality influence glucose metabolism. Short or poor sleep raises cortisol and insulin resistance, which can increase HbA1c. However, the effect is moderate and varies between individuals. An HbA1c test alone cannot diagnose sleep disorders. The evidence is based on observational and small interventional studies, not large RCTs, so its strength is limited. For a complete picture, combine HbA1c with fasting glucose and an oral glucose tolerance test. No single biomarker can replace clinical assessment.